Faint positive 4 weeks after complete miscarriage?

In desperate need for advice. 4 weeks ago I had a complete miscarriage 🙁 I went into the hospital the next day to have my hcg levels checked and they had dropped to 30hcg and 2 days later they were at 12hcg. Now 4 weeks on I am getting a faint positive on pregnancy tests. It took me and my partner 2 years to conceive so you can see why im thinking this may still be something left over from the miscarriage a month ago? I have never used a forum before but the doctors arent very helpful and I could really use some advice.
Best wishes and luck to everyone else ttc
Katie x